The realization that solid structures form mostly as periodic crystalline structures allowed us to describe numerous material properties in nature [1]}. Specifically, as there is only a finite number of possible periodic arrangements in each dimension, we can categorize the material spectral properties (band structures) according to their spatial symmetries. Using this general framework, we obtain an overview of material bulk responses.
In recent decades, concepts originating from the mathematical field of topology bear growing impact on our understanding of material properties [2]}, [3]}. Topology generalizes the notion of symmetry by attributing non-local order parameters (topological invariants) to the material, which are used to classify materials into distinct families. These families cannot be continuously deformed into one another, implying the existence of observable topological phase transitions.
